Processing of pigmented nylon fibers using modified polymers

ABSTRACT

An improved process for melt spinning a pigmented hexamethylene adipamide fiber from a melt blend of a polymer and a colored pigment wherein the polymer is a random interpolyamide or a block polymer having two different difunctional recurring amide-forming moieties other than those which form hexamethylene adipamide is disclosed along with pigmented hexamethylene adipamide polymer fibers having tenacities greater than 7.5 or even 8 grams per denier.

This is a continuation of application Ser. No. 07/616,126, filed Nov.20, 1990, now U.S. Pat. No. 5,223,196.

TECHNICAL FIELD

This invention relates to pigmented nylon fibers made from certainrandom and/or block polyamides and to methods for reducing the drawtension necessary for orienting melt-spun pigmented nylon fibers.

BACKGROUND OF THE INVENTION

Nylon can be dyed with acid or cationic dyes to give colored yarns whichmay be used in fabrics or carpets. Recently, yarn producers have begunincorporating colored pigments into nylon yarns to improve theirresistance to degrading and fading in ultraviolet light, to giveimproved resistance to chemicals and noxious fumes and to give permanentcoloration which is not removed by washing. While some pigments can bemixed easily into the nylon without adversely affecting the filamentspinning operation, most pigments--and particularly organics--cause somedifficulties while being mixed into the nylon or in subsequentmelt-spinning and drawing operations. In general, organic pigments tendto cross-link nylon, change its viscosity, form spherulites which weakenthe fibers, and cause increased draw tension and filament breaks.

Ultraviolet light degrades nylon, and the degradation can be acceleratedby the presence of some pigments. To avoid this, copper in various formsis often added to the polymer. The amount of copper which is effectivein preventing degradation of the polymer by ultraviolet light alsocauses poor spinning performance. The combination of pigment and copperis still worse.

European Patent Publication No. 0373655 ("Anton et al."), published Jun.20, 1990, and incorporated herein by reference, discloses processes formaking stain-resistant, pigment-colored fibers with acceptable levels ofspinning performance. Those processes involve forming a random nyloncopolymer made with up to 4.0 weight percent of a cationic dye additivesuch as 5-sulfoisophthalic acid or its salts, adding up to 4.5 weightpercent of a pigment concentrate to the copolymer, and melt-spinning thepigment/polymer blend. Certain pigments, however, remain very difficultto spin even using the copolymers disclosed therein.

While Anton et al. is directed primarily at pigment-colored fibersuseful in carpet applications, there is also a demand for pigmentedfibers suitable for use in certain industrial applications such as forparachute fabrics, life-jackets, and industrial sewing thread where hightenacity is required. Here too, however, the presence of pigment hasmade it difficult to draw the fibers, and consequently insufficientorientation is obtained to achieve tenacity levels greater than 7.5grams per denier, which is a level that can be attained fornon-pigmented nylon yarns.

Ways of reducing the impact of such pigments on nylon spinning anddrawing performance would permit the use of a wider selection of coloredpigments, both organic and inorganic, would enable fiber producers tooffer a complete range of styling colors while reducing productdeficiencies and operating difficulties, and would allow for theproduction of high tenacity pigmented nylon fibers.

SUMMARY OF THE INVENTION

It has now been found that in a process for melt-spinning a pigmentedhexamethylene adipamide polymer fiber by the steps of forming ahomogenous melt blend of a polyamide and a colored pigment, spinning theblend to form a fiber, and applying tension to the fiber to draw it andthereby increase its orientation, an improvement for decreasing the drawtension necessary to achieve a predetermined degree of draw in the fibercan be obtained by using as the polyamide a random interpolyamide orblock polyamide having at least 80 percent by weight polymerizedhexamethylene adipamide units and having at least two differentrecurring difunctional amide-forming moieties other than those whichform hexamethylene adipamide, each of said different recurringamide-forming moieties being present in an amount of 0.25 to 10 weightpercent of the polyamide and wherein the different amide-formingmoieties constituting part of a block are selected from the groupconsisting of the following radicals: isophthalic, terephthalic,dodecanedioic, 2-methylpentamethylenediamino, and N,N'-dibutylhexamethylenediamino. (For convenience, these will hereinafter bereferred to as the "block-forming moieties".)

In one form of the invention the two recurring amide-forming moietiesare incorporated into the polyamide to be spun by polymerizing a blendof nylon 6,6-forming monomers, i.e. hexamethylene diamine and adipicacid or hexamethylene adipate salt, with 0.25 to 10 weight percent each,preferably 0.4 to 7.5 weight percent each, of two or more differentdifunctional polyamide-forming monomers to produce a randominterpolyamide which is a terpolymer or a multi-polymer. For instance,Example 1 hereinafter illustrates a terpolymer formed by thepolymerization of nylon 6,6 forming monomers, caprolactam, and sodium5-sulfoisophthalate.

In an alternate form the two recurring difunctional amide-formingmoieties are incorporated into the polyamide by melt-blending nylon 6,6homopolymer with one or more different polyamides having block-formingmoieties in the polyamide chain(s). Under suitable conditions of timeand temperature, transamidation occurs and the polyamide chains havingthe block-forming moieties break into shorter chains which form blockswith the chains of the homopolymer. When two different block-formingmoieties are incorporated in the homopolymer in this manner, each beingpresent in an amount of 0.25 to 10 weight percent, the processimprovements of this invention are observed. The two differentblock-forming moieties may be provided by the transamidation of a singlepolymer such as poly(N,N'-dibutyl hexamethylenedodecamide) or by acopolymer such as that of isophthalic acid and terephthalic acid withhexamethylene diamine, or alternatively by melt-blending the homopolymerwith more than one different polyamide, e.g., poly(hexamethyleneisophthalamide) and poly(hexamethylene terephthalamide).

In another alternate form a combination of a random interpolyamide and ablock polyamide can be made by polymerizing a blend of nylon 6,6-formingmonomers with 0.25 to 10 weight percent, preferably 0.4 to 7.5 weightpercent of one different difunctional polyamide-forming comonomer toform a random copolyamide. That copolyamide can then be co-melted with adifferent polyamide having a block-forming moiety in the polyamide chainto form a combined random and block polyamide having at least twodifferent recurring amide-forming moieties other than those which formnylon 6,6. For example, a copolymer can be formed by polymerizinghexamethylene diamine with adipic acid and a small amount of the sodiumsalt of 5-sulfoisophthalate followed by block polymerization with theisophthalic moiety, the latter being provided by a polyamide such aspoly(hexamethylene isophthalamide).

When using different polyamides to form block polyamides, theblock-forming polymer(s) to be co-melted with the principal polymer mayoptionally be present in the form of a concentrate in which the coloredpigment has been preliminarily dispersed. This provides a convenientmeans for introducing different polyamides used to form blocks sinceconcentrates comprised of carriers and other additives are typicallyused to provide more uniform mixing of the pigment particles within themelt-blend.

The reduction in draw tension achieved with the aforementionedimprovements results in process operability which is superior to thatobtained when fibers are spun using pigments with nylon homopolymer orrandom copolymers thereof. In fact, operability often approaches that ofunpigmented nylon homopolymers. In addition, such improvement inprocessability can be achieved without loss of tensile properties.

In a further embodiment of the invention, the reduction in draw tensionwhich can be obtained using these processes permits sufficient increasesin the orientation of pigmented nylon 6,6 fibers to achieve fibertenacity of 7.5 or even 8.0 grams per denier or more, along with moduluslevels of 30-35 grams per denier. Such fiber properties have notpreviously been readily attainable with pigmented polyamide fibers.Accordingly, this invention also encompasses pigmented hexamethyleneadipamide polymer fibers having a tenacity of at least 7.5 grams perdenier, preferably of at least 8.0 grams per denier, the fibers beingcomprised of a polyamide and a colored pigment wherein the polyamide isa random interpolyamide or a block polyamide having at least 80 percentby weight hexamethylene adipamide units and at least two differentrecurring difunctional amide-forming moieties other than those whichform hexamethylene adipamide, each of said different recurringamide-forming moieties being present in an amount of 0.25 to 10 weightpercent of the polyamide and wherein amide-forming moieties constitutingpart of a block are selected from the group consisting of isophthalic,terephthalic, dodecanedioic, 2-methyl pentamethylenediamino, andN,N'di-butyl hexamethylenediamino.

As used herein the term "amide-forming moiety" refers to a diacid,diamine or lactam after removal of the functional end-groups. As alsoused herein "hexamethylene adipamide units" refers to the nylon 6,6units formed from two recurring amide-forming moieties, i.e., thehexamethylene diamino moiety, --(HN--(CH₂)₆ --NH)-- formed from themonomer hexamethylene diamine and the adipic moiety --(OOC--(CH₂)₄--COO)-- formed from the monomer adipic acid. The term "interpolyamide"is used generically to refer to random polyamides comprised of two ormore different recurring units and consequently having at least threedifferent amide-forming moieties as part of the polymer chain. Suchpolyamides would include any random polyamide formed by polymerizing thenylon 6,6 forming monomers hexamethylene diamine and adipic acid withone or more different polyamide forming monomers. The term "copolymer"(or "copolyamide") is used to describe polymers (polyamides) having onlytwo different recurring units with each such unit having an amine and anacid moiety. Accordingly copolymers of nylon 6,6 have three differentrecurring amide-forming moieties. The term "terpolymer" (or"terpolyamide") refers to polymers (polyamides) comprised of threedifferent recurring units, requiring four different amide-formingmoieties. An example of a nylon 6,6 terpolymer would be the reactionproduct of the nylon 6,6 forming monomers with two different comonomerssuch as isophthalic acid and 2-pentamethylene diamine. The term"multipolymer" (or "multi-polyamide") refers to polymers (polyamides)comprised of more than three different recurring units. The term "blockpolymer" or "block polyamide" refers to a polymer obtained by co-meltingand then further processing together two or more different polymers toform blocks containing the recurring amide-forming moieties of each ofthe different polymers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot of process breaks as a function of draw tension forvarious fibers made with dark plum and navy pigment concentrates, thebest-fit straight line through these data showing the directrelationship between draw tension and process breaks.

FIG. 2 is a plot of process breaks as a function of quench area forvarious fibers made with dark plum and navy pigment concentrates, thebest-fit straight line through these data showing the directrelationship between quench area and process breaks.

DETAILED DESCRIPTION

The improved processability of these polyamide fibers can be understoodby analysis of the conditions under which they are melt-spun and drawn.As will be seen in the discussion below, freshly melt-spun pigmentedfilaments of nylon 6,6 homopolymer tend to quench more rapidly thannon-pigmented filaments. Such rapidly quenching filaments both tend tobreak during spinning and require more tension to orient the fiberduring drawing. In turn, increasing the force on the fiber duringdrawing results in increased break levels. As shown in the Examples, thepigment-colored random and block polyamides described herein both quenchmore slowly and require less force to draw, thereby leading to fewerbreaks during processing.

The processes of this invention can be used to produce nylon fibershaving different degrees of orientation and therefore different tensileproperties. As the fibers orientation increases, its tenacity, forexample, is increased. Depending on the tenacity and other fiberproperties needed for a given end-use application, the desired degree oforientation is determined. The total mechanical draw necessary toachieve that level of orientation, and hence the desired fiberproperties, is then set. The freshly-spun fiber is drawn by tensioningit typically between feed rolls and faster-turning draw rolls, the ratiobetween the two (draw ratio) being the measure of the draw and thedegree of orientation being achieved. If the tension on the fiber is toohigh as it is being drawn at any given draw ratio, breaks occur and theprocess is disrupted. It is therefore desirable to reduce the drawtension necessary to achieve a predetermined draw ratio.

Fibers to be used in textile and carpet applications, for example,require comparatively low tensile strength, and the freshly-spun fibersare typically drawn from as little as about 150% for textile yarns toabout 250-300% to provide tensile properties (about 3 grams/deniertenacity and about 65% elongation) suitable for carpet fibers.

For industrial applications however, higher tenacity fibers aredesirable and consequently more orientation is needed. By reducing theforce needed to draw the fibers, higher draw ratios which translate tohigher orientation levels--and therefore higher tenacity levels--can beachieved using these processes. By drawing the fibers in the range of4.5 to 5.5X, pigment-colored polyamide fibers having tenacity levels ofat least 7.5 grams per denier can now be melt-spun from compositions ofa polyamide and a colored pigment concentrate. A preferred combinationfor making such fibers involves the nylon 6,6 interpolyamide made fromnylon 6,6 salt with caprolactam and either 5-sulfoisophthalic acid or asalt thereof, particularly the sodium salt, as comonomers. Aparticularly preferred high tenacity black fiber can be spun undercommercial conditions from a molten composition of a black pigmentconcentrate containing the pigments Channel Black (PBK-7) andIndanthrone Blue (PB-60) and a random terpolyamide made fromhexamethylene adipate to which has been added about 2-4 weight percentcaprolactam and about 1-3 weight percent of the sodium salt of 5-sulfoisophthalic acid. These fibers are useful as woven fabrics forparachute material as well as for high-strength sewing thread and otherindustrial applications.

Suitable difunctional comonomers which may be used with nylon 6,6forming monomers to provide the different recurring amide-formingmoieties found in the random interpolymers used in this inventioninclude aliphatic and aromatic diacids, aliphatic and aromatic diamines,lactams, and the salts formed using such compounds. Examples of suchcompounds include, but are not limited to, isophthalic acid,dodecanedioic acid, 2-methyl-1,5-diaminopentane, m-xylyldiamine,5-sulfoisophthalic acid and its salts, particularly the alkali metalsalts, caprolactam, etc. Based on the wide range of comonomers testedand described in further detail in the Examples below, it would appearthat although certain comonomers appear to be more effective thanothers, any combination of comonomers that polymerize well and can bemelt-spun with nylon 6,6 forming monomers will at least to some degreeassist in counter-acting the processing problems introduced by mostpigments.

Polyamides useful in forming block polyamides with nylon 6,6 and nylon6,6 base polymers in order to achieve the process improvements of thisinvention are those which are capable of providing the specificblock-forming moieties discussed previously. Examples of such polyamidesinclude poly(N,N'-dibutyl hexamethylenedodecamide), copolymers ofisophthalic acid and terephthalic acid with hexamethylene diamine, andpolymers of 2-methyl pentamethylenediamine with isophthalic,terephthalic, dodecanedioic acids, or combinations thereof. Particularlygood results have been obtained by melt-blending nylon 6,6 base polymerswith poly(N,N'-dibutyl hexamethylenedodecamide) and with isophthalicacid/terephthalic acid copolyamides. The nylon 6,6 base polymers may beeither nylon 6,6 homopolymer or copolymers having at least 80 percent byweight hexamethylene adipamide units, a preferred copolymer being therandom nylon 6,6 copolymer of hexamthylene adipamide and up to 4 weightpercent of the sodium salt of 5-sulfoisophthalate.

Such melt-blend block polyamides require at least about 0.25 weightpercent of each amide-forming moiety constituting a block, depending onthe respective polyamides used. In general, however, the amount of acompound required to modify the base polymer sufficiently to obtainimproved spinning performance will be greater when forming a melt-blendblock polyamide than that required when using random ter- ormulti-interpolyamides described above. The precise amount of anamide-forming moiety required within the 0.25 to 10 weight percent rangewill depend on the specific polyamides and the pigment involved, and onthe amount of improvement desired.

The block polymers are formed by melt-blending two or more polyamidesunder conditions of time and temperature suitable for a transamidationreaction (i.e. an amide interchange) between the different polymerchains to occur. The time and temperature can be adjusted to obtainvarying degrees of block formation, but typical melt-spinning conditionsare generally sufficient for some degree of block formation to occur.

While 10 weight percent of the different recurring amide-formingmoieties appears to be a practical upper limit, in some cases amountsgreater than 10 weight percent can be expected to provide improvedprocess performance as well, though the fiber will begin to lose thecharacteristics of the base polyamide involved. Accordingly the upperlimit for each of the recurring amide-forming moieties appears to beconstrained only by cost considerations and end use performancerequirements.

The pigmented yarns made by processes of this invention may be made witha wide range of both organic and inorganic pigments which are generallyintroduced in the form of a concentrate formulation containing one ormore pigments, the number, color, and proportion of which are based onthe final color shade desired, and other materials including one or moreknown polyamide carriers, such as nylon 6 and the terpolymer of nylon6/6,6/6,10 (46/34/20%), as well as lubricants and other polymericadditives.

Among the colored pigments which can be effectively utilized inpolyamide fibers using the processes described herein are those shown inTable A below such as Phthalo Blue (PB-15:2), Perylene Red (PR-179),Indanthrone Blue (PB-60), Phthalo Green (PG-36), Yellow Chromium Complex(SY-21), and those of the Carbon Black (PBK-7) family such as LampBlack, Furnace Black, or Channel Black. Others include Phthalo Blue R/S(PB-15:1), Antimony-Chromium-Titanium Complex (PB-24), Iron Oxide YS andIron Oxide BS (PR-101), Diazo Anthroquinone (PR-177), Cobalt Blue(PB-28), Carbazole Violet (PY-23), Filamid Red 3B (SR-226), Phthalo BlueGIS (PB-16), and Zinc Ferrite (PY-119). All of these pigments can beused either singly or in combinations with one another. As used hereinthe term "colored pigments" is intended to exclude white pigments suchas titanium dioxide which have long been used in small quantities todeluster nylon.

It should be noted that reduced draw tension is also observed whenspinning polyamide fibers from the random and block polyamides describedherein even when using colored pigments which do not create particularlydifficult spinning problems with nylon 6,6 homo- or copolymers. Examplesof such pigments include the iron oxide pigments mentioned above.

In addition to their use in making fibers, the pigment-colored randomand block polyamides described herein may also be useful in a widevariety of non-fiber applications including, for example, films andblow-molded products.

The choice of the comonomers or additive polymers used to achieve theprocessing advantages of the invention will be determined in part by theintended end-use of the polyamide fiber. For example, to improvestain-resistance of a fiber or other product produced from thepolyamide, Anton et al disclose that from 0.5-4.0 weight percent of acationic dye additive such as the sodium salt of 5-sulfoisophthalic acidcan be copolymerized with nylon 6,6 or 6. Accordingly, ifstain-resistant fibers are desired, such cationic dye additives wouldlogically be selected to provide one of the different recurring amidemoieties. However, where use of such an additive may not be desirable inthe final product, such as in end uses where a high degree of aciddyeability is needed (e.g., acid dye over-printing of fabric or carpetor for differentiation with a fiber product which is acid dyestain-resistant), alternative comonomers or additive polymers wouldlogically be selected.

POLYMER FORMATION

The homopolymers and random interpolyamides used herein can be preparedby a variety of polymerization techniques, but condensationpolymerization is the preferred method. A particularly convenient methodused for making the random interpolyamides described in this inventionis to provide two or more aqueous salt solutions, one being the nylon6,6 precursor hexamethylene adipate and the other(s) being precursor(s)for the different recurring unit(s) to be incorporated into the nylon6,6 polymer chain. Such other salt solutions of the comonomers beingused to modify the nylon 6,6 polymer are frequently formed from themodifying comonomer and a balancing amount of a nylon 6,6 monomer. Forexample, when forming a nylon 6,6 copolymer with isophthalic acid orwith a sulfonated isophthalic acid, the salt would be balanced with anequimolar amount of hexamethylene diamine. Similarly, when forming anylon 6,6 copolymer with 2-pentamethylene diamine, the additive saltwould be balanced with an equimolar amount of adipic acid.Alternatively, two different amide-forming moieties can be provided bythe same salt, the salt being formed, for example, by equal molarquantities of isophthalic acid and 2-methylpentamethylene diamine.Suitable quantities of different salt solutions can be mixed to producea composite salt solution for the desired final polymer composition.Alternatively, the nylon 6,6-forming monomers and the modifyingcomonomers used to form the different recurring units of the randominterpolyamide can be added in "neat" rather than salt form, before orduring the polymerization process.

The condensation polymerization can be carried out in a batch orcontinuous reactor. It is usually desirable to add various additives forprocess control. A variety of catalysts are known for use inpolymerizing nylon 6,6 homopolymer such as phenyl phosphonic acid,manganese hypophosphite, etc., and these have been found to be useful inpolymerization of random interpolyamides described herein. Similarly, avariety of antifoam agents can be used to control the foaming in thereaction vessel(s). If desired, other additives can also be added tomeet specific end-use requirements.

The salt solution with desired additives is reacted in a suitablereactor vessel, such as an autoclave, under an inert atmosphere. Thesalt solution is heated to a temperature between 175° and 200° C. whileincreasing pressure to about 300 PSIA to minimize loss of volatileorganic compounds such as hexamethylene diamine. This typically takesabout an hour and allows formation of oligomers. The temperature is thenincreased to between 250° and 275° C. depending on the polymercomposition. The pressure is then released at a slow rate to bleed offsteam and to drive the reaction toward polymerization. While maintainingapproximately the same temperature, the reaction mixture is held at alow constant pressure for a sufficient time to obtain the desired extentof reaction. The polyamide is then extruded from the reaction vessel andconveniently chopped and dried to produce flake. The relative viscosity(RV) of nylon 6,6 interpolymers from the autoclave (as measured with aformic acid solution) can be in the range of 15 to 80, but is generallybetween 20 and 55.

The polyamide flake thus produced can be spun at the RV it is produced,or it can be further polymerized to a higher RV by conventional solidphase polymerization processes (such as by removing water under an inertgas at controlled temperature and humidity). Alternatively, the RV mayalso be increased by other means such as by venting off water as thepolymer is melted in the extruder prior to spinning.

It is possible to add any various known additives such as delustrants,antioxidants, and even pigments, to the polyamide at a suitable point inthe polymer preparation. It is preferred, however, to add the pigment tothe polymer flake as the flake is melted in an extruder in advance ofspinning. This is the preferred method of pigment addition since itresults in good dispersion, avoids contamination of the autoclave vesselwith pigment, and reduces degradation of both the pigment and thepolymer.

Spinning

The polymers used in this invention are typically melted in flake formin an extruder, preferably of the screw melter type. Colored pigment,typically dispersed as a concentrate in a polymeric carrier, is co-fedto the extruder where it is co-melted to provide a homogeneousmelt-blend. Polyamides made from the block-forming moieties previouslydescribed may be used in place of or in addition to the conventionalpigment carriers to provide the moieties used to make the blockpolyamides useful in this invention. Alternatively, such moieties may beprovided in the form of different polyamides separately fed into theextruder along with the pigment and the primary nylon 6,6 homopolymer orcopolymer flake. See Examples 24-25 hereinafter.

Following formation of the homogeneous melt-blend, the pigmented polymermelt is typically pumped through a transfer line to a spinneret, andspun through the spinneret orifices into a quench chimney to formfilaments which are cooled to a non-tacky state by a cross-flow of air.The filaments are pulled through the quench zone by a feeder roll andare withdrawn from the chimney through a steam-conditioner tube. Thefilaments are then drawn to increase their orientation. Various drawingtechniques are known, including the coupled spin-draw process asdescribed in U.S. Pat. No. 4,612,150 (DeHowitt) or the two stage drawprocess described in U.S. Pat. 3,311,691 (Good).

EXAMPLES

The following examples are offered for the purposes of illustrating theinvention and are not intended to be limiting. Percentages are by weightunless otherwise indicated. The test methods which follow were used forobtaining the results described herein.

DESCRIPTION OF TEST METHODS

Formic acid relative viscosity (RV) of the polyamides is measured asdescribed at column 2, lines 42-51 in Jennings, U.S. Pat. No. 4,702,875.

Amine and carboxyl ends are determined by the methods described on pages293 and 294 in Volume 17 of the "Encyclopedia of Industrial ChemicalAnalysis" published by John Wiley & Sons, Inc. (1973).

Denier of the yarn is measured according to ASTM Designation D-1907-80.

Tensile Properties (Tenacity, Modulus, and Elongation) are measured asdescribed by Li in U.S. Pat. No. 4,521,484 at column 2, line 61 tocolumn 3, line 1.

Quench Area--Yarn speeds are measured in the quench chimney at severalpoints on the threadline at various distances from the spinneret.Customarily speeds are measured at twelve locations, starting 9 inchesbelow the spinneret and ending 55 inches below it. Three or fourthreadlines are measured, and the average speeds at each location arecalculated. A graph of yarn speed vs. location is plotted, a curve isfitted to the data, and the area under the curve is then determined. Ahigh value for Quench Area, i.e. a high value for the area under thecurve, correlates with a high potential for poor spinning operability.

Draw Tension is the tension needed to get a predetermined degree of drawin the fiber. It is measured in the draw zone, while the yarn is beingdrawn, using a hand-held tensiometer model number TR 2000 fromTensitron, Inc., Harvard, Mass. Three to four threadlines are measured,and the average draw tension is recorded. Draw ratio, throughput, andyarn temperature will affect the measurement, and must be kept constantwhile draw tension is being measured.

Draw Ratio is an indication of the degree the yarn is being drawn,calculated by dividing the draw roll speed by the feed roll speed. Inthe case of a two-stage draw process wherein there are two draw rolls,the draw roll speed is that of the second draw roll.

Draw Ratio at Break (DRB) is determined by increasing the draw ratio ofthe yarn until the yarn breaks every time it is wrapped around the drawrolls. A low DRB indicates that the yarn cannot be fully orientedwithout breaking, and is therefore an indicator of poor spinning/drawingperformance.

Actual %Draw Tension Effectiveness (%DTE_(act)) is the reductionobtained in draw tension per weight percent of the non-nylon 6,6amide-forming moieties in the random interpolyamide. It is calculated bythe equation: ##EQU1## where: (DT)HP=Draw Tension of Nylon 6,6 WithPigment

(DT)MP=Draw Tension of Modified Polymer with Pigment

(DT)NP=Draw Tension of Non-Pigmented Nylon 6,6

and Wt % Additive The total wt % of non-nylon 6,6 amide-forming moietiesin the interpolyamide

EXAMPLES1-5

Control 1, described in Table B, was prepared by polymerizinghexamethylene adipamide salt of 8.2+0.1 pH by removing water through theconventional condensation polymerization process described above, andthen cutting the polymer into flake. The standard nylon 6,6 flakeproduced had --NH₂ ends of 59 equivalents/106 g polymer and a formicacid relative viscosity (RV) of 41. This polymer was then furtherpolymerized via the solid phase polymerization process, melted using ascrew melter, spun and drawn in a coupled process using a draw ratio of270%, and bulked to form a 1245-denier, 19 dpf product. No pigment wasadded in Control 1.

Various process and product characterization techniques were used toestablish the base line conditions. For example, the velocity(yards/minute) profile of the filaments was measured in the quench zoneas a function of distance from the spinneret and the area under thiscurve is reported in Column 4 of Table B. The force required to draw thefiber as well as the number of quality-related process breaks (QB) perhundred thousand pounds of spun fiber were measured as reported incolumns 5 and 9 respectively. These are typical values for a nylon 6,6process without any pigment.

Control 2 is the same nylon 6,6 polymer, but dark plum pigmentconcentrate having the composition described in Table A was added at thescrew melter at a rate of 1.98% on weight of the fiber and homogeneouslyblended into the polymer melt. The polymer conditions were adjusted tothe same melt viscosity as Control 1, which is measured as the pressuredrop in the transfer line to the spinneret. Both quench area and forceto draw (draw tension) increased significantly, 31% and 84%respectively. This observation is consistent with the hypothesis thatthe pigment interacts with the nylon and substantially changes thequench rate which, in turn, leads to higher draw tension. This change isdramatic enough that the yarn feels brittle. However, the major impactis on spinning performance where the process breaks increasedsubstantially (column 9), depressing the yield to less than 40%.

For Controls 3 and 4 respectively, 5% nylon 6 and 2% sodium5-sulfoisophthalate copolymers of nylon 6,6 were prepared by blendinghexamethylene adipate salt with caprolactam (Control 3) and with a saltformed from equimolar quantities of sodium 5-sulfoisophthalate andhexamethylene diamine (control 4), polymerizing each of the two blends,and cutting the polymers into flake. These modified polymers each had 66parts per million of copper added as cupric acetate prior topolymerization. The RV and --NH₂ ends were 37 and 64 for Control 3 and30 and 57 for Control 4 respectively. Under similar melt viscosity asControl 1 and with dark plum pigment, significant reductions in quencharea, draw tension and breaks were observed, but still these values weresignificantly higher than Control 1, indicating that the effect of thenylon-pigment interaction is not completely eliminated. The %DTE_(act)clearly indicates the superiority of the sodium 5-sulfoisophthalatemoiety over that of caprolactam in terms of reducing draw tension.

The use of a higher level of sodium 5-sulfoisophthalate in the nylon 6,6copolymer further reduces draw tension, quench area, and quality breaksas shown in Controls 5 and 6. However, the polymer casting process andgel formation are a concern with this polymer. In addition, the % drawtension effectiveness reduces as higher levels of this additive areemployed.

In Control 7, a nylon 6,6 copolymer with 1.84% of isophthalic acid wasprepared by blending hexamethylene adipamide salt and hexamethyleneisophthalamide salt, then polymerizing under standard conditions, andcasting into flake. This polymer contained normal additives including 66parts per million copper, added as cupric acetate. As shown in Table Bthe % draw tension effectiveness per percent of the comonomer issignificantly higher than for isophthalic acid than for caprolactam, butsignificantly lower than sodium 5-sulfoisophthalate.

Example 1 is a random terpolymer of nylon 6,6, 3 wt % polymerized unitsof caprolactam, and 2 wt % polymerized units of sodium5-sulfoisophthalate made by blending ingredients in salt form and thenpolymerizing as described previously. The fiber was made with dark plumpigment under identical conditions as controls 5-7. Surprisingly, thedraw tension, the quench area, and quality breaks are significantlyreduced, almost returning to the levels of non-pigmented yarn,Control 1. That is, the nylon-pigment interaction effect is almosteliminated. Even more surprising is the fact that a minor change inpolymer composition effected by blending the nylon 6,6-forming monomerswith comonomers which form two different recurring difunctional amideunits other than the primary hexamethylene adipamide units improves theeffectiveness of the process by reducing draw tension, quench area, andprocess breaks beyond expectations. The synergistic effect of the twodifferent recurring units can be seen by calculating the expected %DTEshown in column 7 of Table B. Based on the %DTE_(act) for Controls 3 and4, it would be expected that each percent of caprolactam would reducethe draw tension by 7.8% and that each percent of sodium5-sulfoisophthalate would reduce the draw tension by 25.9%. The expected%DTE per percent of additive for the polymer of Example 1 wouldtherefore be

    [3(7.8)+2(25.9)]/5=15.04%

Since the %DTE_(act) for the interpolyamide of Example 1 is 19.04, a26.3% synergistic effect is achieved with this particular randomterpolymer.

The random terpolymers of Examples 1A-5 were made in an identical mannerto that of Example 1 except that quantities and types of amide-formingcomonomers used to make the polymers were varied as shown in column 3 ofTable B. By comparing Example 1A with Example 1 it can be seen thatincreasing the level of caprolactam in the random terpolymer from 3% to5%, while still reducing the draw tension as compared to Controls 2 and3, does not offer any further advantage.

Significant synergism was also observed in the random terpolymer ofExample 2 containing 3% caprolactam and 3% sodium 5-sulfoisophthalate,and both quench area as well as process breaks were low compared to thevarious controls.

Similar synergistic effects were observed with the random terpolymerscontaining isophthalic acid and caprolactam (Example 3) and isophthalicacid and sodium 5-sulfoisophthalate (Example 4), and process breaks weresignificantly reduced. Examples 4 and 5 were run with a differentpigment concentrate (navy) than the previous examples and controls (darkplum). Due to the similarities observed between the two colors, valuesfor the dark plum controls were used to calculate the expected %DTE andsynergism shown in Table B for these examples.

FIGS. 1 and 2, respectively, plot the relationships between draw tensionand quench area with process breaks for the data shown on Table B. Itcan clearly be seen that the draw tension and quench area measurementscorrelate well with process breaks. These process characterizationtechniques can be used very effectively in determining the effectivenessof a modified polymer in reducing nylon-pigment interaction, and hence,its effectiveness in reducing process breaks. Use of such techniquesallows one to significantly reduce the development cost and time, forexample, of developing new polymers, new spinning processes, or even newpigments. For the same reasons, these techniques were used in subsequentExamples as discussed below.

                                      TABLE A                                     __________________________________________________________________________           Total Pigment                                                                         Concentrate Components (wt % of Fiber)                                Concentrate   Nylon 6/6,6/6,10                                                                             Carbon                                                                             Anatase          Other               Color  (wt % of fiber)                                                                       Nylon 6                                                                             Terpolymer                                                                             Lubricant                                                                           Black                                                                              TiO2 Pigment 1                                                                           Pigment                                                                             Additives           __________________________________________________________________________    Dark Plum                                                                            1.98    0.99  0.36     0.07  0.03      0.12  0.290 0.12                Navy   2.06    1.03  0.37     0.07  0.03      0.27  0.160 0.12                Electric Blue                                                                        4.97    3.58  0.75     0.05       0.12 0.33  0.150                     Mint   2.00    1.28  0.27     0.03            0.30  0.030 0.09                Black  1.85    0.92  0.37     0.05            0.46  0.005 0.05                __________________________________________________________________________                              Color  Pigment 1   Pigment 2                        __________________________________________________________________________                              Dark Plum                                                                            Phthalo Blue (PB-15:2)                                                                    Perylene Red (PR-179)                                      Navy   Phthalo Blue (PB-15:2)                                                                    Perylene Red (PR-179)                                      Electric Blue                                                                        Phthalo Blue (PB-15:2)                                                                    Indanthrone Blue (PB-60)                                   Mint   Phthalo Green (PG-36)                                                                     Yellow Chromium Complex                                                       (SY-21)                                                    Black  Carbon Black (PBK-7)                                                                      Indanthrone Blue                 __________________________________________________________________________                                                 (PB-60)                      

                                      TABLE B                                     __________________________________________________________________________           Pigment                                                                              Polymer  Quench Area                                                                          Draw Tension                                                                          % DTE                                                                              % DTE Synergism                                                                           Quality Breaks         Item   Concentrate                                                                          (wt % additives)                                                                       (sq yds/min)                                                                         (gpd)   Actual                                                                             Expected                                                                            (%)   /100,000               __________________________________________________________________________                                                           lbs                    Control 1                                                                            None   6,6      694.50 0.894                    100                    Control 2                                                                            Dark Plum                                                                            6,6      911.11 1.647                    >2200                  Control 3                                                                            Dark Plum                                                                            6,6/A(5.0)                                                                             N/A    1.352   7.8              800                    Control 4                                                                            Dark Plum                                                                            6,6/B(2.0)                                                                             800.89 1.256   25.9             1124                   Control 5                                                                            Dark Plum                                                                            6,6/B(3.0)                                                                             749.83 1.191   20.2             370                    Control 6                                                                            Dark Plum                                                                            6,6/B(4.0)                                                                             729.17 1.089   18.5             159                    Control 7                                                                            Dark Plum                                                                            6,6/C(1.8)                                                                             888.69 1.491   11.3             1800                   Example 1                                                                            Dark Plum                                                                            6,6/A(3.0)/B(2.0)                                                                      698.42 0.930   19   15     26.7 134                    Example 1A                                                                           Dark Plum                                                                            6,6/A(5.0)/B(2.0)                                                                      N/A    1.035   11.6 13    -10.8 300                    Example 2                                                                            Dark Plum                                                                            6,6/A(3.0)/B(3.0)                                                                      761.89 0.913   16.2 14     15.7  85                    Example 3                                                                            Dark Plum                                                                            6,6/A(3.0)/C(2.0)                                                                      750.44 1.175   12.5 9.2    35.9 486                    Example 4                                                                            Navy   6,6/B(2.0)/C(1.0)                                                                      769.19 1.185   22   21     4.8  100                    Example 5                                                                            Navy   6,6/A(1.0)/B(2.0)                                                                      729.92 1.245   17.8 19.9  -10.6 700                    __________________________________________________________________________     Additives                                                                     A = Caprolactam                                                               B = Sodium 5sulfoisophthalate                                                 C = Isophthalic Acid                                                     

EXAMPLES 6-9

For this series of Examples a variety of modified random interpolyamideswere prepared by blending salts of hexamethylene adipamide and variouscomonomers to produce co-, ter-, and multipolymer matrices bycondensation polymerization under comparable process conditions to thosedescribed previously. These polymers were then converted to flake andfurther polymerized by solid phase polymerization reaction as describedearlier. The dark plum pigment described in Table A was introduced intoeach polymer before the screw melter except the pigment concentrateaddition rate was kept constant for all polymers at 2.25 wt % of fiber,instead of 1.98 wt % of fiber as described in Table A. No pigment wasadded in Control 8. When transitioning from one polymer type to anotherpolymer type, minor adjustments on solid phase polymerization conditionswere necessary to obtain the same melt viscosity as measured by thepressure drop in the polymer transfer line from the screw melter to thepolymer manifold before the spinning pack.

These polymers were then each extruded through a spinneret and spun,drawn at a draw ratio of 260%, and bulked to form a 1140 denier, square,4 hole hollow filament 17 dpf fiber product using a typical coupledspinning machine and spinning conditions described earlier.Characterization techniques described earlier, like draw tension andquench area, were used to determine the effectiveness of the differentrandom interpolyamides in bringing the process toward conditionscomparable to those observed in the absence of pigment.

Comonomers employed in this series included caprolactam (A), sodium5-sulfoisophthalate (B), isophthalic acid (C), 2-methyl pentamethylenediamine (D), dodecanedioic acid (E), glutaric acid (F), and m-xylenediamine (G). The level of each additive, in wt %, in the final polymeris given in Table C in the third column in parentheses for thesemodified polymers. In making the control polymers, for those having anacid comonomer (Controls 10, 12, and 13) a balancing amount ofhexamethylene diamine was present, while for those having a diaminecomonomer (Controls 11 and 14) a balancing amount of adipic acid waspresent. Example 7 was balanced with adipic acid to obtain the desiredweight percentages of additives, while no nylon 6,6-forming monomer wasrequired to balance the additives present in Examples 6 and 8.

From these results, it can be concluded that different comonomers havedifferent effectiveness in terms of reducing the force required to drawand for reducing the quench area. The draw tension effectiveness of thevarious copolymer controls ranged from about 3% to about 11% (Controls10-14). The effectiveness of these comonomers is substantially improvedwhen more than one is used to make a random terpolyamide ormulti-polyamide, as indicated by the draw tension effectiveness resultsand the calculated synergism values for Examples 6-9. The multipolyamideof Example 9, formed by polymerizing hexamethylene adipamide formingmonomers with caprolactam, sodium 5-sulfoisophthalate (balanced withhexamethylene diamine), 2-methyl pentamethylene diamine balanced withdodecanedioic acid, together with a small amount of the branching agenttris(amino ethyl)amine (TREN), the latter being balanced with adipicacid, was particularly effective. Looking at this particularmultipolymer, it is interesting to note that most of the comonomers usedhave very low effectiveness individually (3-7% for A, D, and E). (Thesodium 5-sulfoisophthalate additive, which is relatively effectiveindividually, is employed at a very low level of 0.4 wt %.) This Exampleclearly demonstrates that even by using comonomers with low individualeffectiveness, the effectiveness of a polymer can be substantiallyimproved by balancing with a random multipolymer system. It is expectedthat the effectiveness would have been even greater if the branchingagent TREN had not been used. It would therefore appear that aparticularly effective random interpolyamide useful for achieving theprocess improvements of this invention involves the use of themulti-polymer formed by polymerizing a composition comprised ofhexamethylene adipamide-forming monomers with caprolactam,5-sulfoisophthalic acid or a salt thereof, 2-methyl pentamethylenediamine, and dodecanedioic acid, the random multi-polyamide so producedhaving 1-3 weight percent polymerized units of caprolactam, at least 0.4weight percent polymerized units of 5-sulfoisophthalic acid or a saltthereof, 1-2 weight percent polymerized units of 2-methyl pentamethylenediamine, and 1-3 weight percent polymerized units of dodecanedioic acid.

Tenacity (gpd) and % elongation of these pigmented fibers were alsomeasured. Column 9 in Table C gives values for the product of Tenacityand the square root of Elongation for the fibers of this series. Thisparameter is thought to be particularly useful in defining the overalldrawability of the fiber. It is apparent that when the pigment is addedto nylon 6,6 homopolymer, T×E^(1/2) reduces by about 30% (Controls 8 and9). This loss in properties is slightly reduced with the copolymersystems of Controls 3-7, but is significantly reduced for the randomterpolymers of Examples 6-8, and virtually eliminated for themultipolymer of Example 9. The improvement in T×E^(1/2) results in astronger fiber as well as one which can be made with fewer processbreaks.

                                      TABLE C                                     __________________________________________________________________________                                    Draw                                                Pigment                                                                              Polymer     Quench Area                                                                          Tension                                                                             % DTE % DTE                                                                              Synergism                                                                           Tenacity ×       Item  Concentrate                                                                          (wt % additives)                                                                          (sq yds/min)                                                                         (gpd) Actual                                                                              Expected                                                                           (%)   sq.                    __________________________________________________________________________                                                           rt.(Elong.)            Control 8                                                                           None   6.6         739.7  0.875                  21.7                   Control 9                                                                           Dark Plum                                                                            6,6         970.8  1.487                  14.0-15.2              Control 10                                                                          Dark Plum                                                                            6,6/C(2.95) 915.9  1.290 10.9             17.0                   Control 11                                                                          Dark Plum                                                                            6,6/D(2.6)  943.5  1.438 3                17.8                   Control 12                                                                          Dark Plum                                                                            6,6/E(2.95) 930.9  1.369 6.5              16.4                   Control 13                                                                          Dark Plum                                                                            6,6/F(3.0)  851.4  1.307 9.8              16.5                   Control 14                                                                          Dark Plum                                                                            6,6/G(2.5)  856.6  1.332 9.4              17.7                   Example 6                                                                           Dark Plum                                                                            6,6/C(2.95)/D(2.06)                                                                       813.1  1.056 14    7.7  81.8  19.4                   Example 7                                                                           Dark Plum                                                                            6,6/D(2.3)/E(2.7)                                                                         870.7  1.287 6.5   4.9  32.6  18.6                   Example 8                                                                           Dark Plum                                                                            6,6/C(2.6)/G(2.4)                                                                         821.1  1.097 12.7  10.2 24.5  20.4                   Example 9                                                                           Dark Plum                                                                            A(2.0)/B(0.4)/D(1.8)/                                                                     794.3  0.966 15.5  7.07 119.7 21.4                                E(1.95)/H(0.075)                                                 __________________________________________________________________________     *Significant variation in numbers due to high break level                     Additives                                                                     A = Caprolactam                                                               B = Sodium 5sulfoisophthalate                                                 C = Isophthalic Acid                                                          D = 2Methyl Pentamethylene Diamine                                            E = Dodecanedioic Acid                                                        F = Glutaric Acid                                                             G = mXylene Diamine                                                           H = Tris(Amino Ethyl) Amine                                              

EXAMPLES 10-14

A series of experiments was also performed with random interpolyamideshaving the compositions described in Table D. Controls 17 and 18 wereprepared using a salt of sodium 5-sulfoisophthalate and a balancingequimolar amount of hexamethylene diamine. The Examples were preparedfrom a combination of hexamethylene adipate salt and the salt formedfrom isophthalic acid and 2-pentamethylene diamine using thecondensation polymerization and solid phase polymerization methodsdescribed earlier. Two different pigment concentrates having thecompositions and addition rates shown on Table A were used. The pigmentaddition was again at the entrance of the screw melter.

The polymer and pigments were then extruded into trilobal filaments witha modification ratio of 2.3 to form a 18 dpf, 1235 denier product usinga coupled spin-draw process at a draw ratio of 265%. Draw tension wasmeasured on-line for each fiber. In addition, a visual inspection undera flashlight in the draw zone was performed to count broken filaments ina three minute time period. This procedure was repeated several times toget an average number of broken filaments reported in Column 7.

The values reported for Control 15 in Table D are actually the averagevalues for non-pigmented yarn for four different polymers, specificallythose used in Control 17/18, Examples 10/12, 11/14, and 13. The valuesreported for Control 16 were not measured but are derived based on theassumption of a linear relation between process parameters or productproperties of the other fibers in this series.

From these and the preceding Examples, it may be observed that:

Pigment Effect: Irrespective of fiber cross-section, tri-lobal or hollowfilament, pigment deteriorates fiber processing performance. Pigmentalso drastically reduces the fiber physical properties (tenacity andelongation) which may reduce its usefulness for various textile, carpet,or industrial end uses.

Polymer Effect: It is observed from Examples 10-14 that increasing theweight percentage of a specific pair of different recurring amide unitshas a significant effect on improved process performance. With polymercontaining 1.5% polymerized units of isophthalic acid and 1.0%polymerized units of 2-methyl pentamethylene diamine, the spinningprocess was inoperable, whereas with polymer containing 4.5% and 3%respectively of the same two additives (Example 14), the spinningprocess operated without any difficulties. This particular randominterpolyamide appears to be of particular interest since the spinningprocess approached that of non-pigmented nylon in quench area, drawtension, and average number of broken filaments. Also, its physicalproperties are significantly better than Controls 17 and 18, indicatinga superior fiber.

The fibers prepared during these experiments were also stain tested,using the staining test method described in Anton et al. Both Controls17 and 18 were non-stainable, whereas the fibers of Examples 10-14 werereadily stainable. Hence, this random interpolymer is particularlyuseful for making pigmented, stainable fiber without encountering majorprocess difficulties. Such fibers are useful in over-printingapplications or can be further dyed to achieve unique colorationeffects.

                                      TABLE D                                     __________________________________________________________________________           Pigment      Polymer  Quench Area                                                                           Draw Tension                                                                          Tenacity ×                                                                      Average No.              Item   Concentrate  (wt % additives)                                                                       (sq yds/min)                                                                          (gpd)   sq. root(Elong.)                                                                      of Broken                __________________________________________________________________________                                                         Filaments                Control 15                                                                           None                  499.2   0.829   22      0.1                      Control 16                                                                           Dk. Plum or Electric Blue                                                                  6,6      638.9   1.525   11.2-12.8                                                                             >100                     Control 17                                                                           Dark Plum    6,6/B(2.0)                                                                             574.8   1.253   15.29   4.5                      Example 10                                                                           Dark Plum    6,6/C(1.5)/D(1.0)                                                                      604.5   1.245   **      >15                      Example 11                                                                           Dark Plum    6,6/C(4.5)/D(3.0)                                                                      501.8   0.839   20.4    0.15                     Control 18                                                                           Electric Blue                                                                              6,6/B(2.0)                                                                             540.8   1.004   18.27   4.5                      Example 12                                                                           Electric Blue                                                                              6,6/C(1.5)/D(1.0)                                                                      583.3   1.249   **      >15                      Example 13                                                                           Electric Blue                                                                              6,6/C(3.0)/D(2.0)                                                                      562.6   1       16.74   7.1                      Example 14                                                                           Electric Blue                                                                              6,6/C(4.5)/D(3.0)                                                                      514.7   0.814   20.9    0                        __________________________________________________________________________     *Estimated based on assumption of linear relationship with polymer            additive                                                                      **Could not be woundup due to high number of breaks                           Additives                                                                     B = Sodium 5sulfoisophthalate                                                 C = Isophthalic Acid                                                          D = 2Methyl Pentamethylene Diamine                                       

EXAMPLES 15-20

The polymers of this series were prepared in a bench autoclave. Thesemodified nylon 6,6 polymers were each prepared by taking a weighedamount of hexamethylene adipate salt and by adding weighed amounts ofthe various comonomers to the autoclave vessel. As in prior Examples,the balance of NH₂ /COOH ends was maintained by adding equimolar amountsof hexamethylene diamine to balance the end groups of sodium5-sulfoisophthalate. Other additives,, such as antifoam agents were alsoadded to the autoclave. The vessel was then sealed and purged withnitrogen 10 times to remove oxygen.

The heat was then turned on and the water evaporation process wasstarted. Initially, the vent valve was kept closed to build the pressureto 250 psi, and the vapor vent valve was kept in automatic control tomaintain the pressure at 250 psi until the polymer temperature in theautoclave reached approximately 285° C. At this time, the vapor ventvalve was opened to reduce the pressure over the next 90 minutes from250 psi to 0 psi while maintaining polymer temperature. At the end ofthe pressure reduction cycle, nitrogen purge was applied to theautoclave at a low rate to remove moisture, and hence, to force theequilibrium to a higher degree of polymerization. After 30 minutes ofnitrogen sweep, higher nitrogen pressure was applied, and the polymerwas forced through an extrusion nozzle to form ribbons. The ribbons werequenched with water and cut into pieces to produce flaked polymer forsubsequent use in the spinning and drawing process to form fiber.

The polymer samples produced in this manner were dried and furtherpolymerized in an oven under nitrogen purge at 18" of H₂ O pressure. Forthis step of solid phase polymerization, the oven was at roomtemperature when the sample was put in the oven. Then, the temperatureof the oven was raised slowly to 170° C. in 2.5 to 3.0 hrs., and held atthis temperature to obtain the desired relative viscosity. The time wasvariable depending on the initial polymer RV and also the type ofadditive. At the end of the constant temperature period, the oven wasturned off and cooled down before removing the flake from the oven. Thefinal RV of the flake was in the range of 51-57.

These polymer samples were tested for use in making high tenacity fiberssuitable for industrial end-uses. The pigment used for this series isdescribed in Table A as mint. The high tenacity fiber samples of thisseries were produced on bench scale equipment where pigment and thepreconditioned polymer flake were premixed and supplied to a screwmelter. The flake-pigment mixture was then melted, extruded through around hole spinneret to form a round cross-section, 7 filament, 45 dtexyarn. The yarn was quenched by controlled temperature air, and a primaryfinish was applied. The filament bundle was then passed over change ofdirection rolls driven by a variable speed motor. Subsequently, thefilament bundle is passed over two sets of draw rolls, again driven byvariable speed motors. The change of direction (feed) rolls were heatedto about 50° C. to increase the temperature of the yarn during drawing,and the yarn is passed over a three meter long plate heated to about200° C. in the second draw zone to aid drawing. The fiber produced bythis process is then wound up as a package.

The total mechanical draw applied to the fiber can be varied byadjusting the draw roll speeds. For each flake type, the samples wereproduced at three different mechanical draw ratios, 4.4x, 4.8x, and5.2x; 4.8 draw ratio is considered to be nominal. Tenacity was measuredon each sample and plotted against the mechanical draw ratio for eachflake type to determine the draw ratio required to obtain 8.0 gpdtenacity as reported in Column 9 of Table E.

In addition, the draw ratio was increased to a point where the filamentbundle breaks due to excessive stress. This procedure was repeatedseveral times (at least 4), and the average consistent value of drawratio at break was determined (Column 7, Table E). Since some fiberorientation occurs in the chimney due to several factors such as airdrag and snub, there is a predraw of the fiber before the mechanicaldrawing step. By measuring the birefringence (Column 5) of the samplescollected on the change of direction roll before the first stage draw,one can determine the predraw as reported in Column 6.

The drawability (Column 8) is the product of predraw (Column 6) and drawratio at break (Column 7). Similarly, total draw for 8 gpd tenacity(Column 10) is also a product of Column 5 and Column 9. The residualdraw (Column 11) is the difference between the drawability and the totaldraw for 8 gpd tenacity. This parameter is of particular importance inevaluating different polymers for fiber manufacturing because itindicates the operating window between the maximum draw a fiber can takeand the process setting at which one will obtain the desired property.As the value of the residual draw increases, the process breaks reducesince one will be operating at a much lower draw ratio to obtain thedesired properties.

Force to draw (draw tension) was measured between the first stage andsecond stage draw roll at 4.8x draw ratio and is reported in Column 4.Except for Control 19, the mint pigment concentrate described in Table Awas used with all the polymers. It is observed that when mint pigment isadded to nylon 6,6 (Control 20 vs. Control 19), the force to draw andpredraw increase significantly on the other hand, the drawabilityreduces substantially and requires higher total draw to obtain desired8.0 gpd tenacity resulting in a lower residual draw. It was alsoobserved that the process was inoperable at 5.2x mechanical draw ratiodue to extremely high break level. No fiber sample could be collected.This confirms that the residual drawability is a good predictor of thepolymer performance. All these observations are consistent with theprevious observations for producing moderate tenacity yarns (˜3.0 gpd),i.e., pigment addition increases draw tension, produces weaker yarn(poorer tensile properties) at a given draw ratio, and significantlyincreases process breaks.

By introducing at least two different recurring amide-forming moietieswhile manufacturing pigmented high tenacity nylon 6,6, it is observedfrom Examples 15-20 lo that while spinning nylon 6,6 homopolymer andmint pigment is discontinuous due to high breaks, it can easily be madeoperable by using modified random interpolyamides having two differentrecurring amide-forming moieties other than those which form nylon 6,6.Moreover, the use of these random interpolyamides permits sufficientorientation to achieve tenacities of 7.5 or even 8.0 gpd in thesepigmented fibers.

                                      TABLE E                                     __________________________________________________________________________                          Draw         Draw      Draw Ratio                                                                           Total                                                                                Resi-                    Polymer  Pigment                                                                              Tension                                                                            Birefrin-                                                                          Pre-                                                                             Ratio                                                                              Drawa-                                                                             for 8 gpd                                                                            for 8                                                                                dual               Item  (wt % additives)                                                                       Concentrate                                                                          (g)  gence                                                                              draw                                                                             at Break                                                                           bility                                                                             Tenacity                                                                             Tenacity                                                                             Draw               __________________________________________________________________________    Control 19                                                                          6,6      None   81   0.00253                                                                            1.085                                                                            6.00 6.51 5.00   5.43   1.09               Control 20                                                                          6,6      Mint   87   0.00415                                                                            1.098                                                                            5.55 6.09 5.09   5.59   0.51               Control 21                                                                          6,6/B(3.0)                                                                             Mint   68   0.00417                                                                            1.097                                                                            6.10 6.69 4.99   5.47   1.22               Control 22                                                                          6,6/B(4.0)                                                                             Mint   71   0.00282                                                                            1.065                                                                            6.60 7.03 5.45   5.80   1.22               Example 15                                                                          6,6/A(3.0)/B(2.0)                                                                      Mint   68   0.00417                                                                            1.097                                                                            6.30 6.91 4.95   5.43   1.48               Example 16                                                                          6,6/C(1.5)/D(1.0)                                                                      Mint   76   0.00247                                                                            1.086                                                                            6.30 6.84 5.03   5.46   1.38               Example 17                                                                          6,6/C(3.0)/D(2.0)                                                                      Mint   70   0.00268                                                                            1.061                                                                            6.40 6.79 5.13   5.44   1.35               Example 18                                                                          6,6/C(4.5)/D(3.0)                                                                      Mint   66   0.00189                                                                            1.047                                                                            6.85 7.17 5.46   5.72   1.46               Example 19                                                                          6,6/B(2.0)/C(1.0)                                                                      Mint   72   0.00268                                                                            1.061                                                                            5.80 6.15 4.87   5.17   0.99               Control 23                                                                          6,6/I(3.0)                                                                             Mint   80   0.00176                                                                            1.039                                                                            6.17 6.41 5.56   5.78   0.63               Control 24                                                                          6,6/J(3.0)                                                                             Mint   76   0.00139                                                                            1.031                                                                            6.07 6.26 5.35   5.52   0.74               Example 20                                                                          6,6/E(3.0)/I(3.0)                                                                      Mint   70   0.00228                                                                            1.052                                                                            6.10 6.41 5.36   5.64   0.77               __________________________________________________________________________     Additives                                                                     A = Caprolactam                                                               B = Sodium 5sulfoisophthalate                                                 C = Isophthalic Acid                                                          D = 2Methyl Pentamethylene Diamine                                            E = Dodecanedioic Acid                                                        I = Dodecane Diamine                                                          J = Lauryllactam                                                         

EXAMPLE 21

Polymers for the series described in Table F, were also prepared in thebench scale autoclave described earlier. For the nylon 6 homopolymer ofControls 25 and 26 a 70% caprolactam solution in water was charged tothe autoclave with other additives and then polymerized by using theprocess described earlier but slightly modified to account for the lowermelting point of poly(e-caproamide) for Control 25. For the polymer ofControl 27 and Example 21, sodium 5-sulfoisophthalate and 2-methylpentamethylene diamine balanced with adipic acid were added to thecaprolactam solution in the autoclave. Polymerization conditions forboth polymers were standard, including the conditioning process.

Both these polymers were spun under identical conditions on bench scaleequipment with and without pigments. The homopolymer ofpoly(e-caproamide) could not be drawn even to 4.4x draw ratio with orwithout pigment. However, the terpolymer having polymerized units ofcaprolactam (major component), sodium 5-sulfoisophthalate (3.0%), and2-methyl pentamethylene diamine could be spun and drawn to 5.2x drawratio. Also, the drawability is significantly higher for this terpolymerwith or without pigment (˜1.3x higher draw). Hence, it is shown that theterpolymer compositions are not only useful for improved processing ofpigmented nylon 6,6 fibers, but are also useful for making pigmented 6nylon fibers. Similar improvements can be expected for other nylons to,in general, improve spinning performance and/or fiber properties.

                                      TABLE F                                     __________________________________________________________________________          Polymer  Pigment                                                                              Draw Tension        Draw Ratio                                                                           Drawa-                                                                              Tenacity at 4.8        Item  (wt % additives)                                                                       Concentrate                                                                          (g)     Birefringence                                                                        Predraw                                                                            at Break                                                                             bility                                                                              Draw                   __________________________________________________________________________                                                           Ratio                  Control 25                                                                          6 Nylon  None   61      0.00236                                                                              1.054                                                                              4.4    4.64  NA                     Control 26                                                                          6 Nylon  Mint   75      0.00218                                                                              1.049                                                                              <4.56  <4.56 NA                     Control 27                                                                          6/B(3)/D(3)                                                                            None   53      0.00138                                                                              1.031                                                                              5.75   5.92  4.95                   Example 21                                                                          6/B(3)/D(3)                                                                            Mint   54      0.00184                                                                              1.042                                                                              5.65   5.88  4.79                   __________________________________________________________________________     Additives                                                                     B = Sodium 5sulfoisophthalate                                                 D = 2Methyl Pentamethylene Diamine                                       

EXAMPLES 22-23

The polymer described earlier in Example 15 was spun and drawn on a twoposition development machine, which is a prototype of a commercialmachine. The polymer, prepared by the process described previously,contained 95 weight percent nylon 6,6 units, 2 weight percentpolymerized units of sodium 5-sulfoisophthalate, and 3 weight percentpolymerized units of caprolactam, as well as 66 ppm copper added ascupric acetate. This polymer was conditioned to about 60 RV by solidphase polymerization, co-fed with the black pigment described in TableA, to a screw melter where it was melted and extruded through a roundcapillary spinneret to form filaments. These filaments were thenquenched by cross-flow air, drawn using the two-stage draw processdescribed in U.S. Pat. No. 3,311,691 (Good). The product was ˜6dtex/filament with a total dtex of 235.

For Controls 23-25 and Example 22 the quench point of the filaments inthe chimney, measured in inches from the spinneret, is the point atwhich the filaments appeared to be solid when touched with an object,such a as screw driver. The draw force or draw tension required to drawthe fiber in the second stage was also measured. Physical properties ofthe fiber on the final package were also measured, includingspecifically tenacity and elongation. Several packages were measured,and the numbers reported herein are the average values. Also, theaverage time between each break for different items was estimated. Theresults are given in Table G. The following observations can be made:

When pigment is added to 6,6 nylon, Control 23 vs. Control 25, the forceto draw increases by about 86%, tenacity reduces by 17%, tenacitymultiplied by the square root of elongation reduces by 18%, and theprocess breaks increase to the point that the process becomesinoperable.

* When the random modified polymer of Example 22 is used with pigment,both the product and the process are comparable to Controls 23 and 24.It is surprising that even with a lower draw ratio, 0.5 gpd highertenacity is obtained when compared with homopolymer (Control 25).

The results of Examples 22 and 23 as compared to Control 25 areparticularly impressive as these yarns were spun on commercial spinningequipment and therefore demonstrate that these modified polyamides canbe used to produce high tenacity fibers under commercial conditions. Itcan be observed from Example 23 that at a draw ratio of 4.8 blackpigmented nylon yarn having a tenacity of 8.1 gpa and a modulus of 35.1can be made, and from Example 22 that at the lower 4.59 draw ratio, atenacity value of 7.49 and a modulus of 31.7 is achieved.

                                      TABLE G                                     __________________________________________________________________________          Polymer                                                                             Pigment                                                                            Quench                                                                             Total                                                                             Draw Tena-                                                                             Tenacity ×                                                                    Time   Mod-                                                                              Elonga-                                                                            Brk                        (wt % Concen-                                                                            Point                                                                              Draw                                                                              Force                                                                              city                                                                              sq. root                                                                            btwn breaks                                                                          ulus                                                                              tion Strength             Item  additives)                                                                          trate                                                                              (inches)                                                                           Ratio                                                                             (g/dtex)                                                                           (gpd)                                                                             Elong.                                                                              (minutes)                                                                            (gpd)                                                                             %    (Newtons)            __________________________________________________________________________    Control 23                                                                          6,6   None 14   4.81                                                                              1.575                                                                              8.4 39.4  300    37.8                                                                              22   17.3                 Control 24                                                                          6,6/A(3.0)/                                                                         None 20   4.71                                                                              1.702                                                                              7.9 40.6  300    33.7                                                                              26.4 16.4                       B(2.0)                                                                  Control 25                                                                          6,6   Black                                                                               8   4.81                                                                              2.872                                                                              7.0 32.1  16-17  26.1                                                                              21   14.1                 Example 22                                                                          6,6/A(3.0)/                                                                         Black                                                                              14   4.59                                                                              1.711                                                                              7.5 37.9  295    31.7                                                                              25.5 15.5                       B(2.0)                                                                  Example 23                                                                          6,6/A(3.0)/                                                                         Black                                                                              14   4.8 N/A  8.1 38.9  N/A    35.1                                                                              23.1 16.8                       B(2.0)                                                                  __________________________________________________________________________     Additives                                                                     A = Caprolactam                                                               B = Sodium 5sulfoisophthalate                                            

EXAMPLES 24-25

Examples 24-25, the results of which are shown in Table H, illustratethe formation of block polymers by using conventional pigmentconcentrates, but co-feeding to the screw melter a different polyamidehaving isophthalic, terephthalic, or 2-methyl pentamethylenediaminemoieties which, following transamidation, form a block with the nylon6,6 copolymer.

In this series a 2.0% sodium 5-sulfoisophthalate copolymer of nylon 6,6made as previously described was mixed with a Phthalo Blue pigment (0.5wt %) dispersed in a concentrate of nylon 6 (1.0 wt %) and 46%/34%/20%nylon 6/6,6/6,10 terpolymer (0.5 wt %) in the screw melter, where it wasmelted and pumped through a transfer line to spinning packs. In Example24 9.75 weight percent of an isophthalic acid/terephthalicacid/hexamethylene diamine copolyamide (number average molecular weight8900) having polymerized moieties of isophthalic acid (4.0 weightpercent) and of terephthalic acid (1.7 weight percent), these moietiesconstituting 5.7 wt % on weight of the fiber was co-fed to the screwmelter. For Example 25 a 9.75 weight percent polymer of isophthalic acid(5.75 weight percent) and 2-methyl pentamethylenediamine (4.0 weightpercent), the polymer having a number average molecular weight of12,700, was co-fed to the melter. In each case the polymer compositionswere held at 287° C. for about 3-4 minutes, and spun into an 18 dpftrilobal filament (2.3 modification ratio), 1235 denier yarn using acoupled process and a draw ratio of 265%. As described previously, thedraw tension was measured for these examples and the lower draw tensionas compared to Control 26 indicates improved spinning performance.

                  TABLE H                                                         ______________________________________                                                                    Moieties                                                          Polymers    Added as                                                 Polymer  Added       Flake Cofed to                                                                          Draw                                           (wt %    via Pigment Screw Melter                                                                            Tension                                 Item   additives)                                                                             (wt % of Fiber)                                                                           (wt % of Fiber)                                                                         (gpd)                                   ______________________________________                                        Control                                                                              6,6/     M(1.0)/N(0.5)                                                                             None      1.185                                   26     B(2.0)                                                                 Example                                                                              6,6/     M(1.0)/N(0.5)                                                                             C(4.0)/O(1.7)                                                                           0.884                                   24     B(2.0)                                                                 Example                                                                              6,6/     M(1.0)/N(0.5)                                                                             C(5.75)/D(4.0)                                                                          0.803                                   25     B(2.0)                                                                 ______________________________________                                         Additives                                                                     B = Sodium 5sulfoisophthalate                                                 C = Isophthalic Acid                                                          D = 2Methyl Pentamethylene Diamine                                            M = Nylon 6                                                                   N = Nylon 6/6,6/6,10 (46%/34%/20%) terpolymer                                 O = Terephthalic Acid                                                    

EXAMPLE 26

This Example demonstrates formation of a block polyamide with a blockforming moiety in the pigment concentrate.

A pigment concentrate containing 25% Phthalo Blue (PB15:2) pigment, 25%of poly(N,N'-dibutylhexamethylene dodecamide), made by polymerizingbutylated hexamethylenediamine and dodecanedioic acid, and 50% nylon6/6,6/6,10 (46%/34%/20%) terpolymer was added through an additive feederat the throat of a twin screw extruder and mixed with a 2% sodium5-sulfoisophthalate random copolymer of nylon 6,6. Thepoly(N,N'-dibutylhexamethylene dodecamide) had a number averagemolecular weight of 2400. The mixed polymer/concentrate was then melted,heated to 285° C., held for 3-4 minutes, spun and drawn at a 2.6 drawratio using a coupled process into a 1225 denier (136 filaments), 2.3modification ratio trilobal cross-section yarn. Yarn speed was 1000 ypm.Rate of pigment concentrate addition was adjusted such that yarncontained (by weight) 0.35 wt % pigment and hence 0.35% of theN,N'-dibutylhexamethylene dodecamide polyamide, which at the 285° C.spinning temperature can be expected to have formed blocks with thecopolymer which have both the N,N'-dibutylhexamethylene diamino and thedodecanedioic moieties. This yarn was spun without breaks for about twohours. A control yarn made in the same manner as the above exampleexcept from a pigment concentrate containing only 25% of the samePhthalo Blue pigment and 75% nylon 6/6,6/6,10 terpolymer would not spin,even at only 0.10% pigments in yarn, without a significant number ofspinning breaks.

EXAMPLE 27

In another test, a dark plum pigment concentrate containing 25% darkplum pigment (a mixture of Channel Black (PBK-7), Phthalo Blue (PB-15:2)and Perylene Red (PR-159) pigments), 25% of the samepoly(N,N'-dibutylhexamethylene dodecamide) used in the previous example,and 50% nylon 6/6,6/6,10 (46%/34%/20%) terpolymer was added through anadditive feeder at the throat of a twin screw extruder and mixed withnylon pellets consisting of a random interpolyamide of (by weight) 98%nylon 6,6 and 2% sodium 5-sulfoisophthalate. The mixedpolymer/concentrate was then melted, heated to 285° C., held for 3-4minutes, spun, and drawn at a 2.75 draw ratio in a coupled process toform a 1225 denier (128 filaments), square hollow filament cross-sectionyarn. Yarn speed was approximately 869 ypm. Rate of pigment concentrateaddition was adjusted such that the yarn contained (by weight) 0.37%pigment and hence 0.37% of the N,N'-dibutylhexamethylene dodecamidepolyamide which at the 285° C. spinning temperature can be expected tohave formed blocks with the copolymer which have both theN,N'-dibutylhexamethylene diamino and dodecanedioic moieties. This yarnspun well without breaks for about two hours, and the draw tensionmeasured was about 1200 gms or about 0.980 gpd. A control yarn made inthe same manner (except using a pigment concentrate containing only28.4% dark plum pigments and 71.6% nylon 6/6,6/6,10 terpolymer would notspin well, and the draw tension measured was about 1450 gms or about1.18 gpd.

We claim:
 1. A pigmented hexamethylene adipamide polymer fiber having atenacity of at least 7.5 grams per denier, the fiber being comprised ofa polyamide and a colored pigment wherein the polyamide is a randominterpolyamide or a block polyamide having at least 80 percent by weighthexamethylene adipamide units and at least two different recurringdifunctional amide-forming moieties other than those which formhexamethylene adipamide, each of said different recurring amide-formingmoieties being present in an amount of 0.25 to 10 weight percent of thepolyamide and wherein the different amide-forming moieties constitutingpart of a block are selected from the group consisting of isophthalic,terephthalic, dodecanedioic, 2-methyl pentamethylenediamino, andN,N'-dibutylhexamethylenediamino.
 2. A fiber of claim 1 wherein thepolymer is a random interpolyamide formed by polymerizing hexamethyleneadipamide forming monomers, caprolactam and either 5-sulfoisophthalicacid or a salt thereof.
 3. A fiber of claim 2 wherein the differentrecurring units of the interpolyamide are from about 2-4 weight percentpolymerized units of caprolactam and from about 1-3 weight percentpolymerized units of the sodium salt of 5-sulfoisophthalic acid.
 4. Afiber of claim 3 wherein the pigment is one or more selected from thegroup of Carbon Black (PBK-7) and Indanthrone Blue (PB-60).
 5. A fiberof any of claims 1-4 having a tenacity of at least 8.0 grams denier. 6.A fiber of claim 1 wherein the polymer is a random interpolyamide havingfrom about 1-5 weight percent polymerized units of isophthalic acid andfrom about 1-5 weight percent polymerized units of 2-methylpentamethylene diamine.
 7. A fiber of claim 1 wherein the polymer is arandom interpolyamide having from about 1-5 weight percent polymerizedunits of 5-sulfoisophthalic acid or a salt thereof and from about 1-5weight percent polymerized units of isophthalic acid.
 8. A fiber ofclaim 1 wherein the polymer is a random interpolyamide having from about1-5 weight percent polymerized units of dodecanedioic acid from about1-5 weight percent polymerized units of dodecane diamine.
 9. A fiber ofany of claim 1, 2, 3, 6, 7, or 8, wherein the pigment is one or moreselected from the group of Phthalo Green (PG-36) and Yellow ChromiumComplex (SY-21).